The Centers for Disease Control and Prevention (CDC) says roughly 1 million people in the United States are diagnosed with shingles each year. They suffer severe pain and a localized blistering rash. For them, it's easy to decide to get a shot that could lessen symptoms that can last months, even years.

For others, the decision may not be so simple. Consider:

Shingles is a reactivation of chickenpox viruses Varicella zoster or Herpes zoster, which can be dormant inside nerve cells for decades after a case of chickenpox. The shingles vaccine is aimed at preventing this reactivation. So far, data shows the shingles vaccine is effective in reducing the occurrence of shingles about half the time. It does better against a longer-lasting pain, called "post-herpetic neuralgia," or PHN, (which can persist after the shingles rash has resolved), preventing it 66 percent of the time.

If shingles recurs despite shots, the medicine may still help reduce the severity and length of zoster episodes. The CDC says those who have had shingles still should get the shot. Why? Because there's a chance the shingles was misdiagnosed the first time, the vaccine's "punch" wanes over time, and some people who have had shingles suffer second episodes.

Help guiding your decision

Anyone who had chickenpox as a child can get shingles. The virus causing chickenpox lingers near nerves and can erupt into shingles at any time in adulthood. Nobody knows what reactivates it.

There's no way to know who will get shingles. But the older you are, the more likely you are to get it. Immune systems become less effective with age. That's why the CDC urges older people to get the shot.

Shingles occurs in two phases. The milder form starts with a rash on the face, neck, or torso. Rashes turn to fluid-filled blisters that crust over and fall off. This usually lasts between three and five weeks. For those with the PHN version of shingles, intense pain comes next. These folks can't stand the touch of clothes or bedding. The pain can continue for months or years.

In the worst cases, vision can be threatened if the affected nerve root supplies a particular nerve to the eye, causing Herpes Zoster Opthalmicus. This requires immediate medical attention.

Shingle rashes can sometimes develop bacterial "super-infections" which, if on the face, may lead to disfiguring scarring.

Some people shouldn't get shingles shots. They include pregnant women; people with immune systems weakened by HIV/AIDS, lymphoma or leukemia, or people taking immune-system suppressing drugs; chemotherapy, and in certain other situations when the immune system is compromised.

Ask your doctor if you should get a shingles vaccine.

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